Field of the Invention
The present invention relates to a traction control device. The present invention particularly relates to a traction device of a vehicle for preventing or suppressing a spin of a driving wheel by controlling an output of an engine.
Description of the Related Art
In a vehicle such as a motorcycle, if a throttle opening degree is increased rapidly at a time of starting and at a time of traveling, a driving wheel (generally a rear wheel) sometimes spins. Accordingly, various types of so-called traction controls for suppressing a spin of a rear wheel (driving wheel) of a motorcycle have been conventionally proposed. For example, there is a traction control in which an ignition timing of an engine is delayed when a spin occurs to suppress an engine output, thereby reducing the spin of a rear wheel. Further, there is a traction control in which a sub-throttle valve is provided, in addition to a main throttle valve, and when a spin of a rear wheel occurs, an opening degree of the sub-throttle valve is throttled regardless of a throttle operation of a driver to suppress an engine output, thereby reducing the spin of the rear wheel. Further, a traction control in which when a spin of a rear wheel occurs, both of the aforementioned delay control and control of opening degree of the sub-throttle valve are carried out, has also been proposed.
Conventionally, a method of traction control includes a method in which a spin is detected from a vehicle speed difference (circumferential speed difference) calculated from rotation speeds of a driving wheel and a driven wheel. However, the method in which the spin is detected from the vehicle speed difference of the driving wheel and the driven wheel, sometimes causes the following problems. For example, in a motorcycle, there exist an allowance of a transmission, a drive chain and the like, and a lot of the other shock-absorbing materials such as a clutch, a wheel, and a tire, between an engine and a driving wheel. For this reason, a certain amount of time is required for transmitting a reaction of the engine to the driving wheel. Accordingly, even if a rotation speed of the engine is rapidly increased at a certain moment, an influence thereof is not immediately transmitted to the driving wheel, and there exists a time lag. Therefore, in the method of detecting the spin by using the vehicle speed of the driving wheel, a determination whether the spin occurs is delayed, resulting in that the increase in the rotation speed of the engine cannot be suppressed quickly. As a result of this, a variation of the rotation of the engine becomes large, and a coarse control with a large behavior of vehicle body is carried out.
Other than the above, a method of detecting a spin by using a rotation speed of an engine and a vehicle speed of a driven wheel, has been proposed (Patent Document 1). With the use of a configuration as above, since it is possible to determine the spin at a moment at which the rotation of the engine is rapidly increased, the problems as described above can be solved. However, the configuration which uses the engine speed causes the following problems. Specifically, when a driver disconnects a clutch to perform a racing operation, the engine speed is increased. Consequently, since it is determined that the spin occurs, the traction control is intervened. As above, in the configuration of using the engine speed, the use of the configuration is limited only to the state where the clutch is connected. Therefore, it is not possible to apply the configuration to a case where the clutch is disconnected as in a time of starting.
Further, in the traction control as described above, it is experientially clarified that in the configuration in which an ignition timing of all cylinders of the engine is simply delayed, a sufficient recovery of grip cannot be expected, and it is better to thin-out a cylinder whose ignition timing is delayed. On the contrary, Patent Document 2 discloses a configuration in which when a spin of a driving wheel is detected, an ignition timing is delayed to reduce an engine output, but, a concrete control method of the ignition timing is not disclosed.
Although Patent Document 3 discloses a configuration in which a delay is caused by performing thinning-out every one ignition, for the purpose of suppressing a knocking, even if this configuration is applied to the traction control, a range of suppression of output is limited to 50% at maximum. For this reason, in a case where a traveling is performed on a road surface with a low friction coefficient and the like, a spin of a driving wheel cannot be prevented. Further, a proper thinning-out rate for a recovery of grip is different in accordance with a specification of an engine, so that a sufficient recovery of grip cannot be expected with the use of the configuration in which the thinning-out is performed every one ignition with respect to all engines.
Further, in the delay control for the suppression of spin, the ignition timing is generally delayed from a point of view of protection of catalyst. In the delay control, since an output can be controlled every ignition, it is possible to perform control with good response characteristic. However, if a delay amount becomes large, there are possibilities that a combustion state is worsened to cause a backfire and an after-burn, and an exhaust-gas temperature is increased, resulting in that the catalyst is damaged. Accordingly, a range of an output reduction realized by the delay control is limited, and it is difficult to deal with a situation where a large output reduction is required, such as a time of traveling on a road surface with a low friction coefficient.
Meanwhile, with the use of the control of opening degree of the sub-throttle valve, a range of an output reduction is large, and there is no possibility of worsening of combustion state and damage of catalyst. However, the control of opening degree of the sub-throttle valve has a problem that the response characteristic is low. Specifically, even if an instruction of throttling the opening degree of the sub-throttle valve is given at a moment of occurrence of spin, it takes a long time to perform operation. Further, since it takes a long time to complete the reduction in output as well, it is difficult to instantaneously reduce the spin. Further, when an instruction of recovery is given, since it takes a long time to recover the output, an acceleration becomes slow, resulting in that a driving performance is lowered.
Patent Document 4 discloses a configuration in which both of the delay control of the ignition timing and the control of opening degree of the sub-throttle valve are carried out, but, the configuration as above causes problems regarding the control of opening degree of the sub-throttle valve. Specifically, since the control of opening degree is conducted even in a case where a spin amount is small and the spin can be reduced only by the delay control, the response characteristic is low.    [Patent Document 1] Japanese Laid-open Patent Publication No. 01-186437    [Patent Document 2] Japanese Laid-open Patent Publication No. 04-72445    [Patent Document 3] Japanese Laid-open Patent Publication No. 2003-3941    [Patent Document 4] Japanese Laid-open Patent Publication No. 62-67257    [Patent Document 5] Japanese Laid-open Patent Publication No. 02-81734    [Patent Document 6] Japanese Laid-open Patent Publication No. 2003-201878    [Patent Document 7] Japanese Laid-open Patent Publication No. 05-1613    [Patent Document 8] Japanese Laid-open Patent Publication No. 63-192927